The invention is directed to formulating a composition that includes a leuco dye and that changes color after exposure to water.
Hot melt wetness indicator compositions are used to provide a visual indication of a change in the state of wetness of the composition and are frequently used in diapers to provide a visual indication that a diaper is in need of changing. Hot melt wetness indicator compositions are often formed with a pH sensitive colorant such as bromocresol green or bromophenol blue. These colorants turn from a first color, such as yellow, to a second color, such as green, as a result of a change in pH.
Leuco dyes have also been used in volatile organic solvent-based color changing compositions. Leuco dyes are dye molecules that have two forms, one of which is colorless and one of which is colored. Leuco dyes are often supplied as solid particles.
Hot melt applicators typically require compositions that are free of particulate in order to properly dispense a hot melt composition. When particles are present in a hot melt composition, the particles can clog the application equipment that is typically used to apply such compositions, can interfere with the definition of the pattern formed when the composition is applied on a substrate, and tend to settle to the bottom of the “pot” or vessel that holds the bulk of the hot melt composition prior to application.
It would be desirable to have a hot melt wetness indicator composition that provides a distinct color change when contacted with an aqueous liquid such as water, urine or saline, and that can be applied using existing hot melt applicator equipment.